Halogenated 9H-Indeno[1,2-b]Pyrazine-2,3-Dicarbonitrile End Groups Based Asymmetric Non-Fullerene Acceptors for Green Solvent-Processable, Additive-Free, and Stable Organic Solar Cells.

Non-fullerene acceptors (NFAs) significantly enhance photovoltaic performance in organic solar cells (OSCs) using halogenated solvents and additives. However, these solvents are environmentally detrimental and unsuitable for industrial-scale production, and the issue of OSCs' poor long-term stability persists. This report introduces eight asymmetric NFAs (IPCnF-BBO-IC2F, IPCnF-BBO-IC2Cl, IPCnCl-BBO-IC2F, and IPCnCl-BBO-IC2Cl, where n = 1 and 2). These NFAs comprise a 12,13-bis(2-butyloctyl)-3,9-diundecyl-12,13-dihydro-[1,2,5]thiadiazolo[3,4-e]thieno[2'',3'':4',5']thieno[2',3':4,5]pyrrolo[3,2-g]thieno[2',3':4,5]thieno-[3,2-b]indole (BBO) core. One end of the core attaches to a mono- or di-halogenated 9H-indeno[1,2-b]pyrazine-2,3-dicarbonitrile (IPC) end group (IPC1F, IPC1Cl, IPC2F, or IPC2Cl), while the other end connects to a 2-(5,6-dihalo-3-oxo-2,3-dihydro-1H-inden-1-ylidene)malononitrile (IC) end group (IC2F or IC2Cl). The optical and electronic properties of these NFAs can be finely tuned by controlling the number of halogen atoms. Crucially, these NFAs demonstrate excellent compatibility with PM6 even in o-xylene, facilitating the production of additive-free OSCs. The di-halogenated IPC-based NFAs outperform their mono-halogenated counterparts in photovoltaic performance within OSCs. Remarkably, the di-halogenated IPC-based NFAs maintain 94‒98% of their initial PCEs over 2000 h in air without encapsulation, indicating superior long-term device stability. These findings imply that the integration of di-halogenated IPCs in asymmetric NFA design offers a promising route to efficient, stable OSCs manufactured through environmentally friendly processes.

Monitoring Redox Processes in Lithium-Ion Batteries by Laboratory-Scale Operando X-ray Emission Spectroscopy.

Tracking changes in the chemical state of transition metals in alkali-ion batteries is crucial to understanding the redox chemistry during operation. X-ray absorption spectroscopy (XAS) is often used to follow the chemistry through observed changes in the chemical state and local atomic structure as a function of the state-of-charge (SoC) in batteries. In this study, we utilize an operando X-ray emission spectroscopy (XES) method to observe changes in the chemical state of active elements in batteries during operation. Operando XES and XAS were compared by using a laboratory-scale setup for four different battery systems: LiCoO2 (LCO), Li[Ni1/3Co1/3Mn1/3]O2 (NMC111), Li[Ni0.8Co0.1Mn0.1]O2 (NMC811), and LiFePO4 (LFP) under a constant current charging the battery in 10 h (C/10 charge rate). We show that XES, despite narrower chemical shifts in comparison to XAS, allows us to fingerprint the battery SOC in real time. We further demonstrate that XES can be used to track the change in net spin of the probed atoms by analyzing changes in the emission peak shape. As a test case, the connection between net spin and the local chemical and structural environment was investigated by using XES and XAS in the case of electrochemically delithiated LCO in the range of 2-10% lithium removal.

Side group dependent room temperature crystallization-induced phosphorescence of benzil based all organic phosphors.

In this work, we report alkoxy substituted benzil based all organic room temperature phosphors which showed crystallization induced phosphorescence (CIP). Nine title compounds were prepared with various alkyl lengths (OCnH2n+1: n = 8-16) and the effect of alkyl side group length on the phosphorescence performance was investigated, as compared to p-anisil. It was found that both phosphorescence quantum yield and lifetime increased concomitantly as the alkyl length increased up to nonyloxy (BZL-OC9). Further increase in the carbon number caused the phosphorescence performance to deteriorate due to greater conformational freedom of the side groups. An incredible quantum yield of 70% was achieved for BZL-OC9. A promising finding is that the increased quantum yield was accompanied by the increase in the lifetime relative to p-anisil, which has been historically challenging. Single crystallography coupled with UV-Vis spectroscopy revealed that a higher level of intermolecular π-π interactions was observed from p-anisil while more alkyl interactions with less intermolecular π-orbital overlap were found for BZL-OC8. As a result, molecular rigidification with less phosphorescence quenching was achieved for BZL-OC8 leading to enhanced performance. A precipitation study on a dichloromethane solution as a function of the content of MeOH (poor solvent) proved that the emission of the BZL-OCn system is truly aggregation-induced. The current work demonstrates that strategic side group engineering could be a promising approach to developing high-performance all organic phosphors as well as improving the properties of existing phosphors.

High-Performance Organic Electrochemical Transistors Achieved by Optimizing Structural and Energetic Ordering of Diketopyrrolopyrrole-Based Polymers.

For optimizing steady-state performance in organic electrochemical transistors (OECTs), both molecular design and structural alignment approaches must work in tandem to minimize energetic and microstructural disorders in polymeric mixed ionic-electronic conductor films. Herein, a series of poly(diketopyrrolopyrrole)s bearing various lengths of aliphatic-glycol hybrid side chains (PDPP-mEG; m = 2-5) is developed to achieve high-performance p-type OECTs. PDPP-4EG polymer with the optimized length of side chains exhibits excellent crystallinity owing to enhanced lamellar and backbone interactions. Furthermore, the improved structural ordering in PDPP-4EG films significantly decreases trap state density and energetic disorder. Consequently, PDPP-4EG-based OECT devices produce a mobility-volumetric capacitance product ([µC*]) of 702 F V-1 cm-1 s-1 and a hole mobility of 6.49 ± 0.60 cm2 V-1 s-1 . Finally, for achieving the optimal structural ordering along the OECT channel direction, a floating film transfer method is employed to reinforce the unidirectional orientation of polymer chains, leading to a substantially increased figure-of-merit [µC*] to over 800 F V-1 cm-1 s-1 . The research demonstrates the importance of side chain engineering of polymeric mixed ionic-electronic conductors in conjunction with their anisotropic microstructural optimization to maximize OECT characteristics.

Design optimization of a flexure spring used in small-sized ultra-precise optical instrument.

Small-sized ultra-precise optical devices require compact compliant ortho-planar springs (COPS) aka. flexure springs, for precise, frictionless linear motion which depends highly on the design. A self-developed arm-hinge-linked design, named "Panto-style" flexure spring was optimized by selecting 5 design parameters (thickness: t, hinge width: W, arm length 1 and 2: L1 and L2, arm angle: Ó¨) and constructing sets of design of experiments (DOEs). Signal-to-noise ratio (SNR) and response surface model (RSM) regression were obtained in terms of axial deformation. The highest response from the main effects plot was the thickness (t), followed by hinge width (W). The angle of the arm (Ó¨), was considered a non-relevant parameter. The parameters optimization was implemented with constraint input and output. Kinetostatic performances (axial/radial deformations, and stress) were predicted, validated, and compared (RSM, KNN, FE simulations, and experiments) using the optimized design. The average value of KNN and RSM (KNN + RSM) increased the accuracy of axial deformation value compared to RSM alone. To conclude, RSM design parameter optimization followed by KNN + RSM has successfully predicted the output results (axial/radial deformation and stress) confirmed both numerically and experimentally.

Investigation of Hole-Transfer Dynamics through Simple EL De-Convolution in Non-Fullerene Organic Solar Cells.

In conventional fullerene-based organic photovoltaics (OPVs), in which the excited electrons from the donor are transferred to the acceptor, the electron charge transfer state (eECT) that electrons pass through has a great influence on the device's performance. In a bulk-heterojunction (BHJ) system based on a low bandgap non-fullerene acceptor (NFA), however, a hole charge transfer state (hECT) from the acceptor to the donor has a greater influence on the device's performance. The accurate determination of hECT is essential for achieving further enhancement in the performance of non-fullerene organic solar cells. However, the discovery of a method to determine the exact hECT remains an open challenge. Here, we suggest a simple method to determine the exact hECT level via deconvolution of the EL spectrum of the BHJ blend (ELB). To generalize, we have applied our ELB deconvolution method to nine different BHJ systems consisting of the combination of three donor polymers (PM6, PBDTTPD-HT, PTB7-Th) and three NFAs (Y6, IDIC, IEICO-4F). Under the conditions that (i) absorption of the donor and acceptor are separated sufficiently, and (ii) the onset part of the external quantum efficiency (EQE) is formed solely by the contribution of the acceptor only, ELB can be deconvoluted into the contribution of the singlet recombination of the acceptor and the radiative recombination via hECT. Through the deconvolution of ELB, we have clearly decided which part of the broad ELB spectrum should be used to apply the Marcus theory. Accurate determination of hECT is expected to be of great help in fine-tuning the energy level of donor polymers and NFAs by understanding the charge transfer mechanism clearly.

Poly(dimethylsiloxane)-block-PM6 Polymer Donors for High-Performance and Mechanically Robust Polymer Solar Cells.

High power conversion efficiency (PCE) and stretchability are the dual requirements for the wearable application of polymer solar cells (PSCs). However, most efficient photoactive films are mechanically brittle. In this work, highly efficient (PCE = 18%) and mechanically robust (crack-onset strain (COS) = 18%) PSCs are acheived by designing block copolymer (BCP) donors, PM6-b-PDMSx (x = 5k, 12k, and 19k). In these BCP donors, stretchable poly(dimethylsiloxane) (PDMS) blocks are covalently linked with the PM6 blocks to effectively increase the stretchability. The stretchability of the BCP donors increases with a longer PDMS block, and PM6-b-PDMS19k :L8-BO PSC exhibits a high PCE (18%) and 9-times higher COS value (18%) compared to that (COS = 2%) of the PM6:L8-BO-based PSC. However, the PM6:L8-BO:PDMS12k ternary blend shows inferior PCE (5%) and COS (1%) due to the macrophase separation between PDMS and active components. In the intrinsically stretchable PSC, the PM6-b-PDMS19k :L8-BO blend exhibits significantly greater mechanical stability PCE80% ((80% of the initial PCE) at 36% strain) than those of the PM6:L8-BO blend (PCE80% at 12% strain) and the PM6:L8-BO:PDMS ternary blend (PCE80% at 4% strain). This study suggests an effective design strategy of BCP PD to achieve stretchable and efficient PSCs.

Substrate-Free Thermoelectric 25 µm-Thick Ag2Se Films with High Flexibility and In-Plane zT of 0.5 at Room Temperature.

Thermoelectric inorganic films are flexible when sufficiently thin. By removing the substrate, that is, making them free-standing, the flexibility of thermoelectric films can be enhanced to the utmost extent. However, studies on the flexibility of free-standing thermoelectric inorganic films have not yet been reported. Herein, the high thermoelectric performance and flexibility of free-standing thermoelectric Ag2Se films are reported. Free-standing Ag2Se films with a thickness of 25.0 ± 3.9 µm exhibited an in-plane zT of 0.514 ± 0.060 at room temperature. These films exhibited superior flexibility compared to Ag2Se films constrained on a substrate. The flexibility of the Ag2Se films was systematically investigated in terms of bending strain, bending radius, thickness, and elastic modulus. Using free-standing Ag2Se films, a substrate-free, flexible thermoelectric generator was fabricated. The energy-harvesting capacity of the thermoelectric generator was also demonstrated.

Simplified Y6-Based Nonfullerene Acceptors: In-Depth Study on Molecular Structure-Property Relation, Molecular Dynamics Simulation, and Charge Dynamics.

Two new Y6 derivatives of symmetrical YBO-2O and asymmetrical YBO-FO nonfullerene acceptors (NFAs) are prepared with a simplified synthetic procedure by incorporating octyl and fluorine substituents onto the terminal 2-(3-oxo-2,3-dihydro-1H-inden-1-ylidene)malononitrile (INCN) moiety. By moving the alkyl substituents on the Y6 core to the terminal INCN moiety, the lowest unoccupied molecular orbital of the YBO NFAs increases without decreasing solubility, resulting in high open-circuit voltages of the devices. Molecular dynamics simulation shows that YBO-2O/-FO preferentially form core-core and terminal-terminal dimeric interactions, demonstrating their tighter packing structure and higher electron mobility than Y6, which is consistent with 2D grazing incidence X-ray scattering and space charge limited current measurements. In blend films, the hole transfer (HT) from YBO-2O/-FO to the polymer donor PM6 is studied in detail by transient absorption spectroscopy, demonstrating efficient HT from YBO-FO to PM6 with their suitable energy level alignment. Despite the simplified synthesis, YBO-FO demonstrates photovoltaic performance similar to that of Y6, exhibiting a power conversion efficiency of 15.01%. Overall, this design strategy not only simplifies the synthetic procedures but also adjusts the electrical properties by modifying the intermolecular packing and energy level alignment, suggesting a novel simplified molecular design of Y6 derivatives.

Full-endoscopic versus microscopic unilateral laminotomy for bilateral decompression of lumbar spinal stenosis at L4-L5: comparative study.

PURPOSE: Full-endoscopic spine surgery for degenerative lumbar diseases is growing in popularity and has shown favourable outcomes. Lumbar endoscopic unilateral laminotomy for bilateral decompression (LE-ULBD) has been used to treat lumbar spinal stenosis (LSS). However, studies comparing LE-ULBD to microscopic ULBD are lacking. This study compared the clinical efficacy and radiological outcomes between the LE-ULBD and microscopic ULBD. METHODS: The study retrospectively enrolled patients undergoing either LE-ULBD or microscopic ULBD for spinal stenosis at the L4-L5 level. The demographic data, operative details, radiological images, clinical outcomes, and complications of patients from the two groups were compared through matched-pairs analysis. The minimum follow-up duration was 24 months. RESULTS: There were 93 patients undergoing either LE-ULBD (n = 42) or microscopic ULBD (n = 51). The patient demographics were similar between the two groups. The LE-ULBD group had significantly less estimated blood loss, less analgesic use, and shorter hospitalization duration (P < .05). The endoscopic group had a significantly lower visual analog scale for back pain at all follow-up intervals compared with the microscopic group (P < .05). There were no significant differences in leg pain or Oswestry Disability Index. The cross-section area of the spinal canal was significantly wider after microscopic ULBD. There were no significant differences in post-operative degenerative changes in disc height, translational motion, or facet preservation rate. CONCLUSIONS: LE-ULBD is comparable in clinical and radiological outcomes with enhanced recovery for single-level LSS. The endoscopic approach might further minimize tissue injury and enhance post-operative recovery.

MRI-based thalamic volumetry in multiple sclerosis using FSL-FIRST: Systematic assessment of common error modes.

BACKGROUND AND PURPOSE: FSL's FMRIB's Integrated Registration and Segmentation Tool (FSL-FIRST) is a widely used and well-validated tool. Automated thalamic segmentation is a common application and an important longitudinal measure for multiple sclerosis (MS). However, FSL-FIRST's algorithm is based on shape models derived from non-MS groups. As such, the present study sought to systematically assess common thalamic segmentation errors made by FSL-FIRST on MRIs from people with multiple sclerosis (PwMS). METHODS: FSL-FIRST was applied to generate thalamic segmentation masks for 890 MR images in PwMS. Images and masks were reviewed systematically to classify and quantify errors, as well as associated anatomical variations and MRI abnormalities. For cases with overt errors (n = 362), thalamic masks were corrected and quantitative volumetric differences were calculated. RESULTS: In the entire quantitative volumetric group, the mean volumetric error of FSL-FIRST was 2.74% (0.360 ml): among only corrected cases, the mean volumetric error was 6.79% (0.894 ml). The average percent volumetric error associated with seven error types, two anatomical variants, and motions artifacts are reported. Additional analyses showed that the presence of motion artifacts or anatomical variations significantly increased the probability of error (χ2  = 18.14, p < .01 and χ2  = 64.89, p < .001, respectively). Finally, thalamus volume error was negatively associated with degree of atrophy, such that smaller thalami were systematically overestimated (r = -.28, p < .001). CONCLUSIONS: In PwMS, FSL-FIRST thalamic segmentation miscalculates thalamic volumetry in a predictable fashion, and may be biased to overestimate highly atrophic thalami. As such, it is recommended that segmentations be reviewed and corrected manually when appropriate for specific studies.

Iron Phosphide Confined in Carbon Nanofibers as a Free-Standing Flexible Anode for High-Performance Lithium-Ion Batteries.

Iron phosphide with high specific capacity has emerged as an appealing candidate for next-generation lithium-ion battery anodes. However, iron phosphide could undergo conversion reactions and generally suffer from a rapid capacity degradation upon cycling due to its structure pulverization. Chemomechanical breakdown of iron phosphide due to its rigidity has been a challenge to fully realizing its electrochemical performance. To address this challenge, we report here on an enticing opportunity: a flexible, free-standing iron phosphide anode with Fe2P nanoparticles confined in carbon nanofibers may overcome existing challenges. For the synthesis, we introduce a facile electrospinning strategy that enables in situ formation of Fe2P within a carbon matrix. Such a carbon matrix can effectively minimize the structure change of Fe2P particles and protect them from pulverization, allowing the electrodes to retain a free-standing structure after long-term cycling. The produced electrodes showed excellent electrochemical performance in lithium-ion half and full cells, as well as in flexible pouch cells. These results demonstrate the successful development of iron phosphide materials toward high capacity, light weight, and flexible energy storage.

Aerobic copper-promoted oxidative dehydrosulfurative carbon-oxygen cross-coupling of 3,4-dihydropyrimidine-1H-2-thiones with alcohols.

An aerobic Cu-promoted oxidative dehydrosulfurative carbon-oxygen cross-coupling of 3,4-dihydropyrimidin-1H-2-thiones (DHPMs) with both aliphatic and aromatic alcohols is described. Together with the ready availability of DHPMs and both alcohols, the method furnishes facile access to biologically valuable 2-alkoxypyrimidines with rapid diversification.

Is it sufficient to treat adult lumbar spinal deformity using anterior lumbar interbody fusion with percutaneous pedicle screw fixation?

Anterior lumbar interbody fusion (ALIF) has been performed for lumbar spinal restoration and stabilization without extensive paraspinal muscle damage or massive bleeding. The authors retrospectively investigated surgical results of multilevel ALIF followed by percutaneous pedicle screw fixation (PPSF) in adult lumbar spinal deformity (ALSD). This study included 28 patients with degenerative lumbar spinal deformity, who underwent selective multilevel ALIF and PPSF between January 2013 and August 2016 at our hospital. Standing X-rays were performed and coronal Cobb angle (CCA) of scoliosis, sagittal vertical axis (SVA), lumbar lordosis (LL), thoracic kyphosis (TK), pelvic tilt (PT), and sacral slope (SS) were measured. Pain and functional assessment were performed using visual analogue scale (VAS) scores for low back pain and leg pain, and Oswestry Disability Index (ODI) scores. CCA, SVA and LL were significantly improved immediately after surgery and relatively well maintained until the last follow-up. After surgery, PT was significantly decreased and SS was increased, respectively. However, cases with SVA > 95 mm or PT > 30° showed a loss of correction in sagittal balance parameters to a greater extent at the last follow-up compared to the group of patients with minor sagittal imbalance. VAS scores for back and radicular pain, and ODI score were significantly decreased at the final follow-up (p < 0.05). Multilevel ALIF with PPSF yielded favorable clinical and radiological outcomes in coronal and sagittal balance without severe surgical mortality or morbidity in patients with ALSD. However, correction loss in sagittal balance was observed in cases with SVA > 95 mm or PT > 30˚.

Optimization for maximum specific energy density of a lithium-ion battery using progressive quadratic response surface method and design of experiments.

The demand for high-capacity lithium-ion batteries (LIB) in electric vehicles has increased. In this study, optimization to maximize the specific energy density of a cell is conducted using the LIB electrochemical model and sequential approximate optimization (SAO). First, the design of experiments is performed to analyze the sensitivity of design factors important to the specific energy density, such as electrode and separator thicknesses, porosity, and particle size. Then, the design variables of the cell are optimized for maximum specific energy density using the progressive quadratic response surface method (PQRSM), which is one of the SAO techniques. As a result of optimization, the thickness ratio of the electrode was optimized and the porosity was reduced to keep the specific energy density high, while still maintaining the specific power density performance. This led to an increase in the specific energy density of 56.8% and a reduction in the polarization phenomenon of 11.5%. The specific energy density effectively improved through minimum computation despite the nonlinearity of the electrochemical model in PQRSM optimization.

Understanding the Electronic Properties of Acceptor-Acceptor'-Acceptor Triads.

In order to develop new organic materials for optoelectronic applications, a fundamental understanding of the electronic properties of specific chromophore combinations must be realized. To that end, we report "model" acceptor (A)-acceptor' (A')-acceptor (A) triads in which the pendants (A') we selected are well-known components of organic optoelectronic applications. Our pendants are sandwiched between two dialkoxyphenazine (A) through an alkyne bond. The A' was systematically increased in electron-deficiency from benzothiadiazole (BTD-P) to naphthalene diimide with octyl (NDI-O-P) or ethylhexyl groups (NDI-EH-P) to perylene diimide with ethylhexyl (PTCDI-EH-P) to assess changes in the electronic properties of the resultant molecules. Characterizations were performed using both experimental and theoretical methods. From optical and cyclic voltammetry, we found that the electron deficiency of each pendant was directly correlated to the energy level of the lowest unoccupied molecular orbital (E LUMO). When examining the simple molecular orbital diagrams produced at the B3LYP/6-31G* level of theory, the LUMOs were, as expected, primarily localized on the more electron-deficient pendants. In terms of the energy level of the highest occupied molecular orbital (E HOMO), the numerical values obtained experimentally also correlated with values obtained computationally. Attempting to construct a simplified model that would explain these correlated values was not as readily apparent, given the disparate physical characteristics of these compounds. For example, BTD-P and NDI-O-P/NDI-EH-P achieved planarity when computationally optimized, but PTCDI-EH-P adapted a "buckled" geometry on the central PTCDI, consequently forcing the attached phenazines out-of-plane. The title compounds showed solvent polarity-dependent fluorescence, which is indicative of intramolecular charge transfer. In conjunction with our theoretical study, the current system can be viewed as an extension of donor-acceptor-donor systems. Thermal properties characterized by differential scanning calorimetry revealed that reversible phase transitions were only observed for BTD-P. In addition, BTD-P was found to be an efficient gelator in 1,1,1-trichloroethane and toluene. The other compounds in this study did not form gels in any of the solvents tested, which may have been a result of the alkyl groups on the pendants hampering the fibrillation process.

Development of two-dimensional piezoelectric laser scanner with large steering angle and fast response characteristics.

We describe a two-dimensional piezoelectric laser scanner designed and tested to obtain a large steering angle of 1° and fast response characteristics of 200 Hz. To overcome the relatively small expansion capability of piezoelectric actuators, the displacement amplification mechanisms with two levers in series are employed to magnify the end tip of the lever which is connected to a 0.5-in. glass mirror. For fast response characteristics, the natural frequencies of the hinge mechanisms were calculated by using the finite element analysis technique. In order to evaluate the performance of the proposed scanner, the hinge mechanism has been manufactured of titanium alloy and the natural frequencies of the hinge mechanism have been measured by sine sweep test. Also, the actual machining test on the burning paper has been done by using a high power laser, and it is shown that the proposed laser scanner is capable of steering the laser beam 1° with a frequency of 200 Hz.

Solution processible MoOx-incorporated graphene anode for efficient polymer light-emitting diodes.

Graphene has attracted great attention owing to its superb properties as an anode of organic or polymer light-emitting diodes (OLEDs or PLEDs). However, there are still barriers for graphene to replace existing indium tin oxide (ITO) due to relatively high sheet resistance and work function mismatch. In this study, PLEDs using molybdenum oxide (MoOx) nanoparticle-doped graphene are demonstrated on a plastic substrate to have a low sheet resistance and high work function. Also, this work shows how the doping amount influences the electronic properties of the graphene anode and the PLED performance. A facile and scalable spin coating process was used for doping graphene with MoOx. After doping, the sheet resistance and the optical transmittance of five-layer graphene were ∼180 Ω sq-1 and ∼88%, respectively. Moreover, the surface roughness of MoOx-doped graphene becomes smoother than that of pristine graphene. Furthermore, a nonlinear relationship was observed between the MoOx doping level and device performance. Therefore, a modified stacking structure of graphene electrode is presented to further enhance device performance. The maximum external quantum efficiency (EQE) and power efficiency of the PLED using the MoOx-doped graphene anode were 4.7% and 13.3 lm W-1, respectively. The MoOx-doped graphene anode showed enhanced device performance (261% for maximum EQE, 255% for maximum power efficiency) compared with the pristine graphene.

Performance Enhancement and Side Reactions in Rechargeable Nickel-Iron Batteries with Nanostructured Electrodes.

We report for the first time a solution-based synthesis of strongly coupled nanoFe/multiwalled carbon nanotube (MWCNT) and nanoNiO/MWCNT nanocomposite materials for use as anodes and cathodes in rechargeable alkaline Ni-Fe batteries. The produced aqueous batteries demonstrate very high discharge capacities (800 mAh gFe(-1) at 200 mA g(-1) current density), which exceed that of commercial Ni-Fe cells by nearly 1 order of magnitude at comparable current densities. These cells also showed the lack of any "activation", typical in commercial batteries, where low initial capacity slowly increases during the initial 20-50 cycles. The use of a highly conductive MWCNT network allows for high-capacity utilization because of rapid and efficient electron transport to active metal nanoparticles in oxidized [such as Fe(OH)2 or Fe3O4] states. The flexible nature of MWCNTs accommodates significant volume changes taking place during phase transformation accompanying reduction-oxidation reactions in metal electrodes. At the same time, we report and discuss that high surface areas of active nanoparticles lead to multiple side reactions. Dissolution of Fe anodes leads to reprecipitation of significantly larger anode particles. Dissolution of Ni cathodes leads to precipitation of Ni metal on the anode, thus blocking transport of OH(-) anions. The electrolyte molarity and composition have a significant impact on the capacity utilization and cycling stability.

Unusual solvent-dependent photophysical and self-assembly properties of NO2 substituted T-shaped phenazines.

This paper investigates the importance of substituent placement when designing low-molecular mass π-organogelators. The electron-deficient NO2 substituent was systematically added to novel T-shaped phenazines to examine electronic as well as assembly properties. This T-shaped molecular platform promotes selective electronic tuning, which can be theoretically analyzed by examining the system's frontier molecular orbitals. Electronic properties were characterized by UV-vis spectroscopy and cyclic voltammetry, and comparisons were made based on number and placement of the NO2 group. Computational chemistry (B3LYP/6-31G*) was employed for geometry optimizations, and to generate molecular orbital diagrams for all systems. The most noticeable influence of NO2 position was found for two molecules with four NO2 groups placed at different locations about the molecule (T-34dNT and T-35dNT). A 0.13 eV difference in ELUMO was observed while EHOMO was not significantly impacted by this change only in NO2 placement. Interestingly and unexpectedly, the photophysical properties and solvent-dependent gelation properties were considerably different for T-34dNT and T-35dNT. T-34dNT exhibited a unique fluorescence (FL) solvatochromism, with FL intensity and maxima dependent on solvent polarity. This result is indicative of intramolecular charge transfer. In addition, long tailing at the solid-state absorption of T-34dNT suggests the presence of intermolecular charge transfer. The gelation of T-34dNT produced chromism ranging from red to orange to yellow when the solvents changed from acetonitrile to ethyl acetate to cyclohexane, respectively. T-35dNT gels in these solvents did not exhibit any of the same properties. Xerogel morphology characterizations were carried out using three different solvents for both T-34dNT and T-35dNT. In the case of T-34dNT, striking differences in the morphology were detected by field-emission scanning electron microscopy (FE-SEM). We conclude that numbers of substituents are not the only consideration in effective molecular design for organogelators, but that substituent position plays a critical role in certain fundamental properties of these systems.